December 19, 2012

Close Sun-Like Star May Host Five Planets, One Habitable One

Astronomers wrote in the journal Astronomy & Astrophysics that one of the closest and most Sun-like stars may actually host five planets.

The star, which lies 12 light-years away and is visible to the naked eye, is the closest single star that has the same spectral classification as our Sun.

Tau Ceti has five planets that are estimated to have masses between two and six times the mass of the Earth, making it the lowest-mass planetary system detected so far.

The astronomers said that one of the planets sits in the habitable zone, which is the distance in which a planet needs to be in order to host life.

Astronomers combined more than 6,000 observations from three different instruments, using new techniques to find a method to detect signals half the size of previously thought possible.

The method helps to improve the sensitivity of searches for small planets and suggests that Tau Ceti is not a lone star, but has a planetary system.

“We pioneered new data modeling techniques by adding artificial signals to the data and testing our recovery of the signals with a variety of different approaches," said Mikko Tuomi from the University of Hertfordshire. "This significantly improved our noise modeling techniques and increased our ability to find low mass planets.”

Hugh Jones from the University of Hertfordshire said they chose Tau Ceti for modeling because they thought it contained no signals, and was an ideal benchmark system to test methods for the detection of small planets.

“Tau Ceti is one of our nearest cosmic neighbors and so bright that we may be able to study the atmospheres of these planets in the not too distant future," said James Jenkins from Universidad de Chile and Visiting Fellow at the University of Hertfordshire. "Planetary systems found around nearby stars close to our Sun indicate that these systems are common in our Milky Way galaxy.”

Scientists have found over 800 planets orbiting other stars, but planets in orbit around the nearest Sun-like stars are of special value to astronomers.

"This discovery is in keeping with our emerging view that virtually every star has planets, and that the galaxy must have many such potentially habitable Earth-sized planets," said Steve Vogt from University of California Santa Cruz. "They are everywhere, even right next door!"

He said they are beginning to understand that Nature seems to prefer systems that have multiple planets with orbits of less than one hundred days.

"This is quite unlike our own solar system where there is nothing with an orbit inside that of Mercury. So our solar system is, in some sense, a bit of a freak and not the most typical kind of system that Nature cooks up," Vogt said.

Chris Tinney from the University of New South Wales said that astronomers may need to start believing that there may well be more planets out there than stars, some of which may be habitable.